Electrically heated garments, or portions thereof, are helpful in combating the effects of cold temperatures on a person subjected to prolonged exposure to the cold. More specifically, a heated garment can prove helpful to persons such as sportsmen, farmers, construction workers, public officials, military personnel, etc., who frequently are exposed to cold weather for prolonged periods of time.
Problems with prior art electronic control systems for electrically heated garments have existed with respect to the ability to heat a plurality of discrete heating zones of the garment independently. Heating different zones individually with a high degree of control is desirable because of the varying rate at which different parts of the body lose heat. The extremities, i.e., hands, feet and head, for example, suffer from a greater heat loss than the torso. In addition, physical activities of the wearer of the garment can cause different parts of his body to generate heat at varying levels. A system which applies the same level of heat to all areas of the garment can therefore produce temperature levels within the garment that are uncomfortable to the wearer.
Prior art electronic control systems, to be able to control the heat applied to various zones of the garment independently, typically require an independent, user actuatable switch for each zone to enable or interrupt the current flowing to its associated heating element or elements. In these systems the control of the wearer over the amount of heat generated by the various heating elements of the suit is quite limited, the heating elements are either fully on or fully off, thereby generating either maximum heat or no heat at all. In some prior art systems, attempts have been made to provide variable control over the heat generated by each heating element by using switches to selectively connect a power source to a plurality of heating elements having different heat generating capabilities or characteristics. In this manner some control is allowed over the amount of heat generated for a particular zone of the garment, but still only in fixed steps.
Another drawback of many prior art heated garments is the fabric used for the garment itself. Ideally, the fabric should be light in weight and not bulky to minimize the loss of flexibility during physical activities of the wearer. The fabric itself should also have excellent insulating capabilities, be stretchable, and be capable of rapidly absorbing and evaporating moisture and perspiration from the skin of the wearer. Many prior art heated garments suffer from a lack of one or more of these features.
In view of the above, heated garments are needed that include carbon nanotubes.